Burglar alarm system



Feb. 23, 1954 HARPER 2,670,466

BURGLAR ALARM SYSTEM Filed March 24, 1950 INVENTOR. 4/? THUR R. HARPERPatented Feb. 23, 1954 UNITED STATE$ OFFICE BURGLAR ALARM SYSTEM ArthurR. Harper, Detroit, Mich, assignor of fifty per cent to W. R. Findlay,Detroit, Mich.

Application March 24, 1950, Serial No. 151,631

(01. MIL-276) 2 Claims. l

The present invention relates to a burglar alarm system of the typewhich is controlled or actuated by the interruption of flow of electriccurrent through a control circuit operatively associated with doors,windows and the like, of the building in which the system is installedwhen unlawful or irregular entry therethrough is at tempted, suchinterruption causing the alarm circuit to be energized, actuating thealarm.

It is among the objects of the present invention to provide a burglaralarm system adapted to receive its primary source of power from theelectric lighting circuit of the building in which the system isinstalled, and which is operable to actuate one or more alarms whencurrent in the control circuit for the alarm is disrupted, and furtherwhich is operable to automatically reset itself on restoration of powerto the lighting circuit if a temporary power failure should occur.

It is a further object of the present invention to provide a burglaralarm system operable on a low voltage circuit adapted to use standardelectrical apparatus, while being suitably designed to insure adequatevoltage to operate said apparatus irrespective of the length of saidcircuits, whereby the alarm system can be constructed and operated inthe most economical manner and the maximum life of the component partwill be insured.

It is still a further object of the present invention to provide aneconomical, low cost burglar alarm system having a portable control unitadapted to receive power from a standard lighting circuit receptacle andoperable to actuate an alarm response to disruption of a low voltagecontrol circuit, whereby said alarm system can he installed in homes orother buildings by other than licensed electricians Other objects ofthis invention will appear in the following description and appendedclaims, reference being had to the accompanying drawings forming a partof this specification wherein like reference characters designatecorresponding parts in the several views.

In the drawings:

Fig. 1 is a perspective view of one embodiment of the present inventionshowing the component parts of the alarm system prior to itsinstallation; and

Fig. 2 is a view showing diagrammatically the wiring circuit for thecomponent parts of the embodiment shown in Fig. 1.

Before explaining the present invention in detail it is to be understoodthat the invention is not limited in its application to the details ofif U construction and arrangement of parts illustrated in theaccompanying drawings, since the invention is capable of otherembodiments and of being practiced or carried out in various ways. Alsoit is to he understood that the phraseology or terminology employedherein is for the purpose of description and not of limitation.

Referring now to the drawings and particularly to Fig. thereof, ahousing it is shown within which is housed the alarm actuating mechanismfor the burglar alarm system. This is a portable unit which has anextension cord [2 adapted to be inserted into an electrical receptaclein the 110 volt lighting circuit of the building within which theburglar alarm system is to be used. An electric cord M is shown pluggedat its one end into the housing it and connected at its other end to aterminal block it. An electrically operated bell It is wired to theterminal lock it by the wires 25]. Also connected to the erminal blockit are control circuit wires 22 which have in their circuit the lockswitch 24, and other control apparatus.

As will be more fully explained hereinafter,

, conductors 22 extend to the various doors,

, light 2% which will be lighted simultaneously with the sounding of thealarm 18. If desired, an extension cord (not shown) may be plugged intothe light receptacle 28 permitting a flood light to be lighted at anyparticular place in the building.

Referring now to Fig. 2, a schematic diagram of the present inventioncan be seen. The electric current for operating the present burglaralarm system is supplied through the con-'- ductors 30 and 32 directlyfrom the lighting circuit of the building. In the circuit formed byconductors 3t and 32, the primary wind.- ing 34 of a step-downtransformer is inter posed, and connected in parallel with the primarywinding is the circuit 355, which contains a light receptacle for thelight bulb 26 and a relay operated switch 38. As can be seen, when theswitch 38 is closed the circuit 36 will likewise be closed causin thelight bulb 25 to be lighted, and conversely when the switch 33 isopened,

the circuit 35 likewise will be opened preventing the light bulb 26 frombeing lighted. As will be more fully explained hereinafter, the relayswitch 38 is controlled by a relay in the control circuit of the burglaralarm system causing the switch 38 to be closed when the control circuitis interrupted.

The secondary winding 46 of the transformer is included in the controlcircuit'having the switches 42, which are connected respectively,adjacent the various doors, windows and the like, through which unlawfulor irregular entry is to be prevented and are adapted to be :opened :tointerrupt the control circuit should. such entry be attempted. Thecontrol circuit'comprises the secondary winding All, the conductor 44,the switches :22, a relay switch 46, conductortdrelay E1, resistor 52,and conductor 5%. Also in the control circuit, arranged in parallel-with the switches 42 and the relay switch lit, is the conductortii withthe lock switch 24 therein. The lock switch 24 is normally closed whenthe lock to the door or the like, in which the switch is located, isunlocked.

An alarm circuit isprovided which includes the conductor 54, thesecondary winding of the transformer to the center'tapfifl, theconductor 62, relay switch lit, the bell alarm It. The, relay switch fil as well as the relay switch 46in the control circuitv and therelay-switchtii in the lighting circuit are controlledby the relay 5t.When the relay 59 is tie-energized, the relay switches 33 and 6d arenormally closed while the relay switches is open. Thus, it can be seenthat the alarmlli and theilight 'Zt'iwill be actuated whenever the relay5!) is de-energized.

During such periods of time when the burglar alarmsystem is not to beinoperation, the lock containing the lockswitch 24 will be unlockedcausing the'switch 24 to-be closed providing a closed circuit for therelay 5% causing the switches 38 and 66 to be maintained in an openposition so that the light 28 and bell 58 will not be operatedandcausingswitch it to be closed.

When it is desired to place the alarm system in operation, the variousswitches 42 will be closed as well as the switch At which normally isheld in a closed position by the relay til, the-latter :being energizedby virtue of lock switch 24 being closed. The lock switch 211 will thenbe opened so-that the circuit through the switches ill and 46 will bethe only source of supply for energizing the coil 59, and thereafter ifany of the switches 42 shouldbe opened by an unlawful or irregularentry, the control circuit will be disrupted causing the-relay 59 to bedeeenergized, with the result that the switchestt and Gal will beclosed, setting-oh" the alarm.

An added feature of the above control circuit is that the burglar alarmsystem cannotbe left in an inoperative condition after the lockswitch24'. has been locked. If any of the switches :32 have been inadvertentlyleft open, the alarm will sound immediately when the lockcontaining thelock switch 2s has been closed. Thisznecessarily follows, sinceimmediately after said. lock is closed, the lock switch 24' willbeopened. causing the relayfifl to be ,de-energized. If suchaa conditionshould "occur, a check of thevarious switches 42 can be made toascertain-which one is open, and when this switch: has been closed, thebuilding mayabeproperly locked withthe alarm system in operation.

The present burglar alarm systernalso has :provisions made tore-energize thev relay. Eitshould-a temporary power failure occurcausing the entire alarm system to be de-energized. As is believedreadily apparent, if the entire system becomes tie-energized, the relay46 will be opened and since the circuit containing the relay switch 46is the only circuit available to supply current to the relay 5% when thealarm is set, once this switch has been opened the relay coil 55) willnot thereafter automatically be reeenergized on restoration-"of power.For this reason, an auxiliary circuit is provided for controlling therelay switch 53 which is in circuit with the conductor .liJ-.-arrangedin a parallel relationship with the circuit containing the switches andAs can =be seen, if this relay switch is normally closed when the relaycontrolling it is de-energized, in the. event of. a power failure, theswitch 68 will close and on restoration or" the power, the relayElly/illbare-energized through the conductor ill. Thus, current willflow from secondary winding 40: through conductorsdswand it, relayswitch -E38,thro-ugh relay t9 and resistcrt t, andback to secondarywinding 43 via conductor E l.

The auxiliary circuit also includes the resistor l2, relay switch KM,"relay it and conductor 7-8. On restoration of-power after thefailureand after relay 5i] has been re-energized thereby closing relayswitch lt, current will then flow from secondary winding :lllthrough-switches-M and st, via conductor iki to resistor i2, switchl l,relay it, conductor is and baclrto secondary winding is by way ofconductor E l. In this manner relay it will here-energized causing'relayswitches 33 and E ite reopen. .The auxiliary circuit also includes relayswitch -82 and conductor 33. When relay-it is initiallyre-energized theswitch 82 will be closed simultaneously with the opening of relayswitches efi and E4. 'Closing of relay switch 82 completes a circuitthrough relay it so as to maintain the latter'energized. Thus, acircuitis completed whereby current flows from secondary winding lilthrough conductors 62 and to relay switch 82, through relay l8 and backto secondary winding lt via conductors lsand 54. It can be seen thatthis causes the relayfic to remain open so as not toeffestthe operationof the control circuit for controlling the flow of current through therelay-53'.

The step-down transformer withthe. center tap is utilized-to provide 24volts throughthe control circuit while maintaining 12 volts in-thealarmcircuit and the auxiliary circuit. It-is desirable to use 12 voltcircuits so. thatstandard electrical equipment, such as 12 volt relaysmay be used. l-lowever, it is found necessary to use a higher voltagethrough the controlv circuit because of the voltage drop therein which,if a 12 volt circuit were used, might not provide proper actuation of threlays. The resisters; 52 and 72 are placed in series with the relaysStand 16 to prevent overheating of the re ays when energized by the 24volt circuits.

Thus, it can be'seen that a portable-alarm system is provided which canbe installed by one who is not a licensed electrician and can'be easilyinstalled at a relatively lowcost. The burglar alarrn'system is adaptedto actuateboth a visual and an audible alarm, and cannot be accidentlyleft in an inoperative condition. Further, in the event of a temporaryinterruption of velectric power,-such as may result fronran electricalstorm or the like, the alarm'system Willbe automatically reset when thepower; is restored to the system.

Having, thus described .my invention, a I; claim;

1. A burglar alarm system comprising an alarm and a circuit therefor, acontrol circuit including in series therein the winding of a controlrelay, a plurality of switches adapted to open when entry through adoor, window or the like is attempted and a first contact of said relayclosed by the relay winding when it is energized, the alarm circuitincluding therein a second contact of said relay closed when the relaywinding is de-energized, a lock switch in parallel with the saidswitches and the first relay contact for independently energizing therelay winding so that lawful entry may be made through said door orwindow without causing the alarm circuit to be closed, all of the saidcircuits being fed from a single source of power, so that in case offailure of the source of power the relay winding will be de-energizedand will not be able to be re-energized, upon restoration of the sourceof power, due to the opening of the first relay contact and the alarmwill not operate in the absence of power from said source, and means forrestoring said relay by momentarily re-energizing said winding when thepower is restored comprising a relay having a winding connected to thepower source and having a contact closed in a re-energizing circuit forthe first relay independent of the first relay contact when the secondrelay is de-energized.

2. A burglar alarm system as claimed in claim 1 which includes aportable unit in which said relays and their respective contacts arehoused, said unit having a conductor adapted to be connected to thesingle source of power for feeding all of said circuits.

ARTHUR R. HARPER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 492,478 Sturts Feb. 28, 1893 1,158,146 Olney Oct. 2-6, 19151,238,823 Roeder Sept. 4, 1917 1,365,693 Hess Jan. 18, 1921 1,845,621Morrison Feb. 16, 1932 2,191,926 Lemire Feb. 27, 1940 2,225,464 SantinoDec. 17, 1940 2,243,804 Howton May 27, 1941 2,346,171 Laford Apr. 11,1944 2,419,957 Laford May 6, 1947 2,440,002 Bower Apr. 20, 19482,491,987 Lefcourt Dec. 20, 1949

